arXiv subjects

Andrew S Wills

Publications and source records attributed to Andrew S Wills.

2 recordsLinked to original sources

arXiv2016

A historical introduction to the symmetries of magnetic structures: Part 1. Early quantum theory, neutron powder diffraction and the colored space groups

This paper introduces the historical development of the symmetries for describing magnetic structures culminating in the derivation of the black and white and colored space groups. Beginning from the Langevin model of the Curie law, it aims to show the challenges that magnetic ordering presented and how different symmetry frameworks were developed to meet them. As well as explaining core ideas, later papers will show how the different schemes are connected. With these goals in mind, the maths related is kept to the minimum required for clarity.

cond-mat.mtrl-sci↗

arXiv2011

Spin dynamics in the S =1/2 kagome compound vesignieite, Cu3Ba(VO5H)2

We report the study of high quality samples of the frustrated S = 1/2 kagome antiferromagnet vesignieite, Cu3Ba(VO5H)2. Neutron powder diffraction measurements evidence the high quality of the kagome lattice and show no sign of a transition to long-range order. A kink in the susceptibility below T = 9 K is matched to a reduction in paramagnetic-like correlations in the diffraction data and a slowing of the spin dynamics observed by MuSR. Our results point to an exotic quantum state below 9 K with coexistance of both dynamical and small frozen moments \sim 0.1 \muB. We propose that Dzyaloshinsky-Moriya interaction is large enough in this system to stabilize this novel quantum ground state.

cond-mat.str-el↗